Creating scalable web sites that can handle many simultaneous requests and still provide fast experience for each user is hard. Historically, the industry was not differentiating Scalability and Performance, but with emergence of front-end engineering, new field of Web Performance Optimization was born and it became critical to approach them separately. Sergey Chernyshev will compare these two directions of web engineering and describe the differences between them, he will also cover current performance trends and describe different approaches to take in order to measure and analyze Web Performance in comparison to traditional methods that are successfully used to test scalability of web systems.